When should I test with a pregnancy test?

Home pregnancy tests are based on a very simple principle and work by measuring the presence of the hormone HCG (human chorionic gonadotropin) in a woman's urine. HCG (human chorionic gonadotropin) is a glycoprotein hormone secreted by the developing placenta shortly after fertilization. Hence, the presence of this hormone in the urine detects pregnancy.

When should I test with a pregnancy test?

It is ideal to wait until the first day of your missed period before taking a home pregnancy test as most doctors recommend. This is usually around two weeks after conception. However, some tests are more sensitive than others and can be taken earlier. It is essential that you follow all instructions religiously and interpret the results correctly for accuracy in home pregnancy tests. Usually, if all care has been taken, these pregnancy tests are 97% accurate. A blood pregnancy test administered by your doctor is more sensitive than the early home pregnancy tests and can be taken between seven and twelve days after you conceive.

The sensitivity of a home pregnancy test determines when pregnancy can be detected by the pregnancy test. Concentrations of Human Chorionic Gonadotropin (hCG) are reported in milliInternational Units (mIU) or amounts equal to 1/1000th of an IU per milliliter. Pregnancy tests with a sensitivity of 20 mIU/ml are more sensitive than tests with 50 to 100 mIU/ml. With 20 - 25 mIU/ml tests, high sensitivity equates to early detection of pregnancy. Hence you can begin testing accurately as early as eight days after conception.

If you are pregnant, the amount of Human Chorionic Gonadotropin (hCG) in your system should be around 25 mIU at 10 days past ovulation, 50 mIU at 12 days past ovulation, 100 mIU at around two weeks days past ovulation. Blood tests can determine pregnancy as low as between 5 to 10 mIU/hCG, though with levels of 5 mIU, a confirmed determination of pregnancy cannot be made without risking a false positive because as low levels Human Chorionic Gonadotropin (hCG) can be present in the body without pregnancy.

Home pregnancy tests generally detect pregnancy at 50 mIU - 100 mIU Human Chorionic Gonadotropin (hCG), though you can find early-detection pregnancy tests on the Internet with sensitivity levels as low as 20 mIU. With all diagnostic products, take care to follow the instructions. For earliest detection of pregnancy, use first morning urine, as this sample contains the most concentrated amount of Human Chorionic Gonadotropin (hCG). If using first morning urine is not possible, avoiding urination for several hours before using a pregnancy test. Frequent urination can decrease the amount of Human Chorionic Gonadotropin (hCG) in your urine, interfering with early-detection.

If you take a test too early, you may get a false negative (when the test says you are not pregnant but you are). Your body needs time for the hormone to rise to a high enough level to be detected in a test. If the test comes back negative but you still think you could be pregnant, wait a few days and try again. False positives (when the test says you're pregnant but you're not) are possible, but rare. A positive pregnancy test is a pretty good indication that you are pregnant.

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Early Signs of Pregnancy
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